Minghao Hu

Staged multi-cluster fracturing in horizontal wells is a key technology for efficiently developing unconventional oil and gas reservoirs. Extreme Limited-Entry Fracturing (ELF) and Temporary Plugging Fracturing (TPF) are effective techniques to enhance the uniformity of fracture stimulation within a stage. However, in fractured reservoirs, the propagation morphology of multiple intra-stage fractures and fluid distribution patterns becomes significantly more complex under the influence of ELF and TPF. This complexity results in a lack of theoretical guidance for optimizing field operational parameters. This study establishes a competitive propagation model for multiple hydraulic fractures (HFs) within a stage under ELF and TPF conditions in fractured reservoirs based on the Displacement Discontinuity Method (DDM) and fluid mechanics theory. The accuracy of the model was verified by comparing it with laboratory experimental results and existing numerical simulation results. Using this model, the influence of ELF and TPF on intra-stage fracture propagation morphology and fluid partitioning was investigated. Results demonstrate that extremely limited-entry perforation and ball-sealer diversion effectively mitigate the additional flow resistance induced by both the stress shadow effect and the connection of natural fractures (NFs), thereby mitigating uneven fluid distribution and imbalanced fracture propagation among clusters. ELF artificially creates extremely high perforation friction by drastically reducing the number of perforations or the perforation diameter, thereby forcing the fracturing fluid to enter multiple perforation clusters relatively uniformly. Compared to the unlimited-entry scheme (16 perforations/cluster), the limited-entry scheme (5 perforations/cluster) yielded a 37.84% improvement in fluid distribution uniformity and reduced the coefficient of variation (CV) for fracture length and fluid intake by 54.28% and 44.16%, respectively. The essence of the TPF is non-uniform perforation distribution, which enables the perforation clusters with large fluid intake to obtain more temporary plugging balls (TPBs), so that their perforation friction can be increased and their fluid intake can be reduced, thereby diverting the fluid to the perforation clusters with small fluid intake. Deploying TPBs (50% of total perforations) at the mid-stage of fracturing (50% time) increased fluid distribution uniformity by 37.86% and reduced the CV of fracture length and fluid intake by 72.54% and 58.39%, respectively. This study provides methodological and modeling foundations for systematic optimization of balanced stimulation parameters in fractured reservoirs.

Unconventional reservoirs are characterized by low porosity, low permeability, and limited hydrocarbon abundance, making them economically unviable for production under natural conditions. Large-scale hydraulic fracturing has emerged as a critical technology for enabling the effective development of these resources. The three-dimensional development of platform wells employs batch drilling and batch fracturing techniques. By implementing simultaneous fracturing or zipper fracturing approaches, the process achieves well placement, fracturing, and fracture placement in a single step, thereby reducing costs and improving operational efficiency. Platform well fracturing (PWF) involves numerous parameters that require optimization, and the underlying physical processes are highly complex, presenting significant challenges to the design and control of fracturing strategies. To address these challenges, this study focuses on the following aspects: (1) identifying key parameters in PWF and reviewing prior optimization efforts that use production capacity and net present value as objective functions; (2) systematically comparing numerical simulation methods for modeling fracture propagation and simulating production performance, highlighting their role in linking fracturing parameters to objective functions; (3) evaluating the strengths and limitations of single-factor analysis, orthogonal experimental design, and intelligent automatic optimization methods, and proposing a high-dimensional intelligent optimization workflow for fracturing design; (4) examining the technological challenges of PWF and suggesting future directions for its development. This study provides valuable insights into the selection of optimization methods for PWF schemes and offers guidance for advancing the technology’s development, contributing to more efficient and effective resource recovery from unconventional reservoirs.